1. Field of the Disclosure
This disclosure relates to a dye-sensitized solar cell and a fabricating method thereof, and more particularly to a dye-sensitized solar cell with a solution capable of being selectively printed on the surface of a metal oxide nano-particle and to a method of fabricating the same.
2. Description of the Related Art
To meet recent increasing energy demands, a variety of solar cells have been developed which convert solar light energy into electrical energy. The solar cells include CIGS (copper indium gallium (di)selenide) solar cells, silicone-based solar cells, dye-sensitized solar cells, semiconductor solar cells, and so on.
In general, the solar cell generates electron-hole pairs within its semiconductor by external light. Among the electron-hole pairs, the electrons move to an n-type semiconductor and the holes move to a p-type semiconductor, by an electric field generated between the p-type and n-type semiconductors. Accordingly, electrical power is produced.
The solar cells use sunlight which regards as an infinite source. As such, the solar cells are pro-environmental unlike the other energy sources. Also, silicon solar cells are recently in the spotlight of entire world due to an energy problem after being primarily developed in 1983.
The silicon solar cells cause a sharp competition between nations due to a silicon supply problem, thereby increasing their manufacturing costs. Also, many countermeasures are being proposed by domestic and foreign research institutes, but it is difficult to deal with the above problems. As a countermeasure for dealing with the sharp energy problem, a dye-sensitized solar cell has been proposed by a MG (Micheal Grazel) institute within EPEL (Ecole Polytechnique Federale de Lausanne) in Switzerland.
The dye-sensitized solar cell, as a solar cell with optical, electrical and chemical properties, is configured to include sensitive dye molecules and a transition metal as main materials unlike the silicon solar cell. The sensitive dye molecules can generates electro-hole pairs by absorbing visible rays. The transition metal is used for transmitting the generated electrons.
Such a dye-sensitized solar cell has a lower manufacturing cost in comparison with the modern silicon solar cells. Also, the dye-sensitized solar cell can be applied to the outer glass windows of buildings, greenhouse and so on, because of their transparent electrode.
In accordance with an electro transmission system of the dye-sensitized solar cell, the electron-holes pairs are generated in the dye molecules which are excited by light. A part of the electrons included in the electron-hole pairs is drifted to a transparent electrode (hereafter, “transparent cathode electrode”) through drifting paths, which are formed by an interface between metal oxide nano-particles, before being supplied to an external resistor (i.e., an external circuit as a load) via the transparent cathode electrode. On the other hand, the residual electrons are drifted toward the other transparent electrode (hereinafter, “transparent anode electrode”) and returned to the dye molecules by a redox reaction of an electrolyte between the metal oxide nano-particles and the transparent anode electrode. As a factor affecting a conversion efficiency of the solar cell in the electron transmission system, it is that the electron and hole must be easily separated from each other in the excited state of the dye molecule as well as the separated electron must be drifted to the transparent cathode electrode through the path between the metal oxide particles without any resistance. Particularly, if it is a defect in an electron drift path, the loss of electrons is caused. However, since the general metal oxide nano-particle has a diameter range of about 10˜20 nm and a layer formed by the metal oxide nano-particles has a thickness range of 10˜15 μm, it is difficult to prepare the electron drift path without any defect.
To address the above matter, a single element solar cell (hereinafter, “single solar cell”) has been proposed which includes a metal oxide film formed in a thickness range of several to several tens nanometer on the surfaces of nano-particles. The metal oxide film on the surface of the nano-particle is formed using a titanium dioxide solution of weak viscosity which is ordinarily used as a post-processing solution. The titanium dioxide solution cannot be selectively printed due to its week viscosity. As such, the titanium dioxide solution can be applied to the single solar cell, but cannot be applied to a solar cell module which is configured with metal electrode layers divided into the number of solar cells. This results the fact that the metal oxide film is formed on the electrode so as to increase an internal resistance and lower the output efficiency when the titanium dioxide solution is applied to the solar cell module.
Therefore, it is necessary for a solution capable of being selectively printed on only a desired region and used in the formation of a metal oxide film, in order to greatly improve the conversion efficiency of a dye-sensitized solar cell module and prevent the conversion efficiency deterioration, which corresponds to a sharp disadvantage, in large-sized dye-sensitized solar cell modules.